Sealing of cement based grout lines (not glazed tiles) with a penetrating or impregnating sealer is recommended to prevent the penetration of urine, moisture and soil into the porous material and subsequent bacterial growth, odor and discoloration. This assumes a good, non-slip ceramic tile is in place, as is most appropriate for rest rooms and ease of cleaning. If you are faced with resilient tile rest room floors, as most ... — Lynn E. Krafft, ICAN/ATEX editor